The present invention relates to an acceleration-detecting type gyro apparatus, which is suitable for use in mobile objects such as automobiles, ships, or airplanes, for detecting an angular velocity, or angular change, and acceleration relative to the inertial space. More particularly, the present invention relates to an extremely small acceleration-detecting type gyro apparatus in which a gyro rotor is being supported by electrostatic supporting forces in a floating state.
Referring to FIG. 1 to FIG. 5, an example of a conventional gyro apparatus will be described. This gyro apparatus has been disclosed in the Japanese published application No. HEI-7 (1995)-125345, filed on May 24, 1995 by the same applicant as the present application. Refer to the above application for the detailed description.
Referring to FIG. 1, this gyro apparatus will be described. The gyro apparatus comprises: a thin disk-like gyro rotor 20; and a gyro case 21 with the gyro rotor 20 housed therein.
XYZ coordinates for the gyro apparatus are set as shown in the figure. The Z axis is set upwardly along the central axis of the gyro apparatus, and the X axis and the Y axis are set perpendicular to the above Z axis. A spin axis of the gyro rotor 20 is disposed along the Z axis.
As shown in FIG. 1A, the gyro case 21 comprises: an upper bottom member 22, a lower bottom member 24, and a spacer 23 which connects the both, and the spacer 23 has an inner annular wall 23A. Thus, a disk-like closed cavity 26 in which the gyro rotor 20 is housed is formed within the gyro case 21 with the inner surfaces of the upper bottom member 22 and the lower bottom member 24, and the inner wall 23A of the spacer 23. The cavity 26 has been evacuated by a suitable method.
A concave portion 23B is formed outside of the inner annular wall 23A of the spacer 23, and the concave portion 23B is connected to the cavity 26 through a passage 23C. The height of the passage 23C may be from 2 to 3 micrometers. A getter 33 is disposed in the above concave portion 23B, whereby it is possible to maintain the cavity 26 at a high degree of vacuum for a long period of time.
The gyro rotor 20 is formed with a conductive material. For example, single crystal silicon may be used as such conductive material. By using the single crystal material, a gyro rotor with less thermal deformation, smaller influence by secular change, and higher accuracy may be provided. The upper bottom member 22 and the lower bottom member 24 of the gyro case 21 are formed with a non-conductive material, for example, with glass. The spacer 23 may be formed with the same material as that of the gyro rotor 20.
As shown in the right halves of FIGS. 1A and 1B, a plurality of annular electrode portions 200A, 200B, 200C, 200D; and 200Axe2x80x2, 200Bxe2x80x2, 200Cxe2x80x2, 200Dxe2x80x2 are concentrically formed on the upper surface and the lower surface of the gyro rotor 20. Specifically, a plurality of annular grooves 200a, 200b, 200c, 200d; and 200axe2x80x2, 200bxe2x80x2, 200cxe2x80x2, 200dxe2x80x2 are concentrically formed on the upper and lower surfaces, whereby protruding annular electrode portions are formed.
Driving electrode portions 200E, 200Exe2x80x2 are formed at the inner side of the annular electrode portions 200A, 200B, 200C, 200D; and 200Axe2x80x2, 200Bxe2x80x2, 200Cxe2x80x2, 200Dxe2x80x2 on the upper and lower surfaces of the gyro rotor 20. The driving electrode portions 200E, 200Exe2x80x2 are formed between two concentric annular grooves 200d, 200e; and 200dxe2x80x2, 200exe2x80x2 as a plurality of sectorial protruding portions, and may be annularly disposed in a row along the circumference.
Displacement-detection electrode portions 200F and 200Fxe2x80x2 are formed in the center portion, that is, at the inner side of the driving electrode portions 200E and 200Exe2x80x2 on the upper and lower surfaces of the gyro rotor 20. Concave portions 200f, 200fxe2x80x2 are formed in the center portion of the above displacement-detection electrode portions 200F, 200Fxe2x80x2.
The annular electrode portions 200A, 200B, 200C, 200D and 200Axe2x80x2, 200Bxe2x80x2, 200Cxe2x80x2, 200Dxe2x80x2; the driving electrode portions 200E, 200Exe2x80x2; and the displacement-detection electrode portions 200F, 200Fxe2x80x2, all of which are formed as a protruding portion on the upper, and lower surfaces of the gyro rotor 20, may be formed coplanar with each other.
On the other hand, as shown in the left halves of FIGS. 1A and 1B, at least three pairs of electrostatic supporting electrodes, in the present example, a first, second, third, and fourth pairs of electrostatic supporting electrodes 221, 231, 222, 232, 223, 233, and, 224, 234 are disposed on the inner surface of the upper bottom member 22 and the lower bottom member 24 of the gyro case 21. The four pairs of electrostatic supporting electrodes are spaced with every ninety-degree to each other along the circumferential direction. For example, the first and third pairs of the electrostatic supporting electrodes 221, 231, and, 223, 233 are disposed along the X axis, and the second and fourth pairs of electrostatic supporting electrodes 222, 232, and, 224, 234 are disposed along the Y axis.
Individual electrostatic supporting electrodes comprise a pair of comb-shaped portions. For example, the electrostatic supporting electrode 223, which is formed on the inner surface of the upper bottom member 22, in the third pair of electrostatic supporting electrodes 223, 233 is shown on the left side of FIG. 1B. This electrostatic supporting electrode 223 includes two comb-shaped portions 223-1, 223-2 spaced apart from each other, and the above two comb-shaped portions are spaced apart from each other.
One comb-shaped portion 223-1 comprises a radius portion 223R extending in the radial direction, and a plurality of circumference portions 223A, 223C extending in the circumferential direction. Similarly, the other comb-shaped portion 223-2 comprises a radius portion 223R extending in the radial direction, and a plurality of circumference portions 223B, 223D extending in the circumferential direction. The circumference portions 223A, 223C; and 223B, 223D of individual comb-shaped portions 223-1, 223-2 are alternately disposed. Terminal portions 223Rxe2x80x2, 223Rxe2x80x2 are formed at the edge of the radius portions 223R, 223R of the comb-shaped portions 223-1, 223-2, respectively.
Driving electrodes 225, 235 are formed on the inner side of four pairs of electrostatic supporting electrodes 221, 231, 222, 232, 223, 233, and, 224, 234 on the inner surface of the upper bottom member 22 and the lower bottom member 24 of the gyro case 21, respectively. The above driving electrode 225, 235 may be configured to be a plurality of sectors which are annularly disposed in a row along the circumference.
Displacement-detection electrodes 226, 236 are formed in the center portion, that is, on the inner side of the driving electrodes 225, 235 on the inner surfaces of the upper bottom member 22 and the lower bottom member 24 of the gyro case 21.
Hereinafter, sizes and relative positions between the annular electrode portions 200A, 200B, 200C, 200D and 200Axe2x80x2, 200Bxe2x80x2, 200Cxe2x80x2, 200Dxe2x80x2 of the gyro rotor 20; and the electrostatic supporting electrodes 221, 222, 223, 224, and 231, 232, 233, 234 of the upper bottom member 22 and lower bottom member 24 of the gyro case 21 will be described.
With regard to the gyro rotor 20, the outer diameter D, the thickness t, and the mass may be 5 mm or less, 0.1 mm or less, and 10 milligrams or less, respectively. Four annular electrode portions 200A, 200B, 200C, 200D; and 200Axe2x80x2, 200Bxe2x80x2, 200Cxe2x80x2, 200Dxe2x80x2 are shown in FIG. 1. However, a number of annular electrode portions are formed in actual practice. For example, when the width L of each electrode portion in the radial direction is about 10 micrometers, and the above electrode portions are formed at an equal pitch of about 20 micrometers, about 100 annular electrode portions are formed in an annular area with a width of about 2 mm along the radial direction. Here, the width L of each electrode portion and the pitch between the potions in the radial direction are preferably as small as production methods will permit.
The sizes of the electrostatic supporting electrodes 221, 222, 223, 224, and 231, 232, 233, 234 of the upper bottom member 22 and the lower bottom member 24 of the gyro case 21 may be determined corresponding to those of the annular electrode portions 200A, 200B, 200C, 200D; and 200Axe2x80x2, 200Bxe2x80x2, 200Cxe2x80x2, 200Dxe2x80x2. For example, as shown in FIG. 1, the circumference portions 223A, 223C; and 223B, 223D of individual comb-shaped portions 223-1, 223-2 of the third electrostatic supporting electrode 223 are described under assumption that the number of the above circumference portions is four. However a number of circumference portions are formed in actual practice. For example, when the width L of each circumference portion in the radial direction is about 10 micrometers, and the above circumference portions are formed at an equal pitch of about 20 micrometers, about 100 circumference portions are formed in an annular area having a width of about 2 mm along the radial direction.
Hereinafter, relations between positions of the electrode portions of the gyro rotor 20 and the electrostatic supporting electrodes of the gyro case 21 will be described. For example, the relations between positions of the electrode portions 200A, 200B, 200C, 200D; and 200Axe2x80x2, 200Bxe2x80x2, 200Cxe2x80x2, 200Dxe2x80x2 of the gyro rotor 20, and the third pair of electrostatic supporting electrodes 223, 233 will be described. The first circumference portions 223A, 233A of the third pair of the electrostatic supporting electrodes 223, 233 are corresponding to the first electrode portion 200A, 200Axe2x80x2 of the gyro rotor 20, and the second circumference portions 223B, 233B of the third pair of the electrostatic supporting electrodes 223, 233 are corresponding to the second electrode portions 200B, 200Bxe2x80x2. Similarly, the third and fourth circumference portions 223C, 233C; and 223D, 233D are corresponding to the third and fourth electrode portions 200C, 200Cxe2x80x2; and 200D, 200Dxe2x80x2, respectively.
The space xcex4 between the electrode portions of the gyro rotor 20 and the corresponding electrostatic supporting electrodes of the gyro case 21 may be several micrometers, for example, xcex4=2 to 3 micrometers.
Each electrode portion 200A, 200B, 200C, 200D; and 200Axe2x80x2, 200Bxe2x80x2, 200Cxe2x80x2, 200Dxe2x80x2 of the gyro rotor 20 are concentrically disposed relative to the corresponding circumference portions 223A, 233A, 223B, 233B, 223C, 233C; and 223D, 233D of the electrostatic supporting electrodes 223, 233, and, at the same time, they are disposed inwardly or outwardly deviated in the radial direction.
For example, the width and the pitch of each electrode portion 200A, 200B, 200C, 200D; and 200Axe2x80x2, 200Bxe2x80x2, 200Cxe2x80x2, 200D xe2x80x2 of the gyro rotor 20 are equal to those of circumference portions 223A, 233A, 223B, 233B, 223C, 233C; and 223D, 233D of the electrostatic supporting electrode 223, 233, and the both are disposed, inwardly or outwardly deviated from each other in the radial direction by a predetermined distance.
The reason why the electrostatic supporting electrodes according to the present example are alternately disposed will be described. According to the above described configuration, the capacitance between each pair of the comb-shaped portions and the corresponding electrode portions of the gyro rotor 20 is equal on the upper and lower sides of the gyro rotor 20. For example, the capacitance between the first comb-shaped portions 221-1 (221A, 221C) and the corresponding first and third electrode portions 200A, 200C of the gyro rotor 20 is equal to that between the second comb-shaped portions 221-2 (221B, 221D) and the corresponding second and third electrode portions 200C, 200D of the gyro rotor 20 at the first electrostatic supporting electrode 221 in the first pair of the electrostatic supporting electrodes 221, 231, and the value of the capacitance is C1A.
Therefore, the electric potential of the gyro rotor 20 may be always adjusted to zero by setting both the control direct-current voltage applied to the first comb-shaped portion 221-1 (221A, 221C) and the control direct-current voltage applied to the second comb-shaped portion 221-2 (221B, 221D) to be the voltage which has the same magnitude and different polarities, for example, xc2x1V1A. Referring to FIG. 4, the above setting will be later described again.
The second electrostatic supporting electrode 231 in the first pair of electrostatic supporting electrodes 221, 231 will be the same as described above. Moreover, the second, third, and fourth electrostatic supporting electrodes 222, 232, 223, 233, and 224, 234, are also the same as described above.
Here, the driving electrode portions 200E, 200Exe2x80x2, and displacement-detection electrode portions 200F, 200Fxe2x80x2 of the gyro rotor 20, and the corresponding driving electrode 225, 235, and displacement-detection electrode 226, 236 of the gyro case 21 may be shaped in the same manner and disposed at the same position with each other in the radial direction.
Dischargeable stoppers 127, 128 are respectively provided at the central portion of the inner surfaces of the upper bottom member 22 and the lower bottom member 24 of the gyro case 21, that is, in the central portion of the displacement-detection electrodes 226, 236, respectively. The above stoppers 127, 128 are disposed corresponding to the concave portions 200f, 200fxe2x80x2 formed in the central portion of the upper and lower surfaces of the gyro rotor 20.
The dischargeable stoppers 127, 128 are provided so that the displacement in the Z-axis direction, and the displacement in the X-axis and Y-axis directions of the gyro rotor 20 are restrained; the gyro rotor 20 is prevented from being contact with the inner surface of the gyro case 21; and, at the same time, electrostatic charges which have been accumulated in the gyro rotor 20 are discharged.
When the gyro rotor 20 is displaced in the Z-axis direction to approach the inner surface of the gyro case 21, the dischargeable stoppers 127, 128 come in contact with the bottom of the concave portions 200f, 200fxe2x80x2 of the gyro rotor 20 before the electrode portion of the gyro rotor 20 comes into contact with the electrode of the gyro case 21. Moreover, when the gyro rotor 20 is displaced in the X-axis or Y-axis direction, the dischargeable stoppers 127, 128 come in contact with the circumferential inner surfaces of the concave portions 200f, 200fxe2x80x2 of the gyro rotor 20 before the gyro rotor 20 comes into contact with the circumferential inner wall 23A of the gyro case 21.
Accordingly, the gyro rotor 20 is restrained from being displaced in the Z-axis direction, the X-axis direction, and the Y-axis direction, and the gyro rotor 20 is prevented from being contact with the inner surface of the gyro case 21. Further, when the gyro rotor 20 is stopped and grounded, the dischargeable stoppers 127, 128 come in contact the concave portions 200f, 200fxe2x80x2 of the gyro rotor 20, whereby electrostatic charge accumulated in the gyro rotor 20 is discharged to the outside through the dischargeable stoppers 127, 128.
The electrostatic supporting electrodes 221, 231, 222, 232, 223, 233, and 224, 234; the driving electrodes 225, 235; and the displacement-detection electrodes 226, 236, all of which are formed on the upper bottom member 22 or the lower bottom member 24 of the gyro case 21, may be electrically connected to an external power source, or an external circuit by through hole connection. Small holes, that is, through holes are provided in the upper bottom member 22 or the lower bottom member 24, and metal films are formed on the inner surface of the through holes. The electrostatic supporting electrodes, the driving electrodes, and the displacement-detection electrodes are connected to an external power source or an external circuit by the above metal films.
A preamplifier 35, for example, a field-effect type transistor is disposed on the outer surface of the upper bottom member 22, and the above preamplifier 35 is connected to the displacement-detection electrodes 226, 236 as shown in FIG. 1A. Through holes 22A (only a through hole 22A provided on the upper bottom member 22 is shown in the figure) are provided on the upper bottom member 22 and the lower bottom member 24, and the preamplifier 35 is connected to the displacement-detection electrodes 226, 326 by the thin metal film formed on the inner surface of the above through hole 22A.
Furthermore, each of the pair of comb-shaped portions is electrically connected, as described later referring to FIG. 3. Accordingly, for example, through holes 22B (only one through hole is shown in the figure) are provided, corresponding to each of the terminal portions 223Rxe2x80x2, 223Rxe2x80x2 of the comb-shaped portions 223-1, 223-2 of the first electrostatic supporting electrode 223 in the third pair of the electrodes, and a thin metal film formed on the inner surface of the above through hole 22B is connected to a common terminal provided outside of the upper bottom member 22, whereby the terminal portion 223Rxe2x80x2, 223Rxe2x80x2 of two comb-shaped portions 223-1, 223-2 are electrically connected. Similarly, through holes 24A (only one through hole is shown in the figure) are provided, corresponding to each of the terminal portions 231Rxe2x80x2, 231Rxe2x80x2 of the comb-shaped portions 231-1, 231-2 of the second electrostatic supporting electrode 231 in the first pair of the above electrodes, and a thin metal film formed on the inner surface of the through hole 24A is connected to a common terminal provided outside of the lower bottom member 24, whereby the terminal portion 231Rxe2x80x2, 231Rxe2x80x2 of two comb-shaped portions 231-1, 231-2 are electrically connected.
FIG. 2 shows an example of a control loop of the gyro apparatus. The control loop according to the present example comprises a restraining control system including a restraining control unit 150, a rotor drive system including a rotor driving unit 160, and a sequence control unit 170.
The restraining control unit 150 in the present example comprises: a displacement-detection circuit, that is, a preamplifier 35, by which a displacement-detection electric current iP is detected, and the detected current is converted into a displacement-detection voltage VP; and a control operation unit 140 to which the above displacement-detection voltage VP is input, and control direct current voltages xc2x1V1A through xc2x1V4A, xc2x1V1B through xc2x1V4B are generated. Displacement-detection alternating-current voltages AC1A through AC4A, AC1B through AC4B are added to the control direct-current voltages xc2x1V1A through xc2x1V4A, xc2x1V1B through xc2x1V4B, which have been output by the control operation unit 140, and the voltages after the addition are supplied to the electrostatic supporting electrodes 221 through 224, 231 through 234. Further, the gyro apparatus according to the present example is provided with a gyro-acceleration-output calculation unit 145, to which an output signal from the control operation unit 140 is input.
The gyro rotor 20 is supported and restrained in a floating state at a predetermined reference position by applying the control direct-current voltages xc2x1V1A through xc2x1V4A, xc2x1V1B through xc2x1V4B to the electrostatic supporting electrodes 221 through 224, 231 through 234. The displacement-detection electric current iP flows through the displacement-detection electrodes 226, 236 which are formed on the inner surface of the gyro case 21 by applying the displacement-detection alternating-current voltages AC1A through AC4A, AC1B through AC4B to the electrostatic supporting electrodes 221 through 224, 231 through 234. The above displacement-detection electric current iP is converted into the voltage signal VP by the preamplifier 35. The above voltage signal VP includes all the linear displacements and the rotational displacements of the gyro rotor 20.
The control operation unit 140 detects a displacement xc2x1xcex94X in the X-axis direction, a displacement xc2x1xcex94Y in the Y-axis direction, and a displacement xc2x1xcex94Z in the Z-axis direction, and a rotational displacement xcex94xcex8 and xcex94xcfx86 around the Y axis and the X axis of the gyro rotor 20 (The direction of the arrow shown in the upper right of FIG. 3 is assumed to be positive), using the voltage signal VP. Further, the control direct-current voltages xc2x1V1A through xc2x1V4A, xc2x1V1B through xc2x1V4B required to the electrostatic supporting electrodes 221 through 224, 231 through 234 are calculated, using the above displacements. Thus, the control direct-current voltages xc2x1V1A through xc2x1V4A, xc2x1V1B through xc2x1V4B are changed, and the gyro rotor 20 is returned to the original position so that an amount of deviation becomes zero.
The control loop or the restraining system according to the present example is not a passive type, but an active type system, considering that the amount of deviation of the gyro rotor 20 is measured in actual practice, and electrostatic forces are actively changed so that the above deviation becomes zero.
Referring to FIG. 3, the operation of the restraining control system will be described in detail. The gyro rotor 20 is rotating at a high speed in actual practice, and four parts at positions corresponding to the first, second, third, and fourth pairs of the electrostatic supporting electrodes in the gyro rotor 20 are assumed to be P1, P2, P3, and P4, respectively.
FIG. 3 is a cross sectional view of the gyro apparatus according to the present example, taken along the XZ plane, in which the first and third pairs of electrostatic supporting electrodes 221, 231; and 223, 233, disposed along the X axis, and the first and third parts P1, P3 of the gyro rotor 20 corresponding to the above electrodes, are shown. Although the second and fourth pairs of electrostatic supporting electrodes disposed along the Y axis, and the second and fourth parts P2, P4 of the gyro rotor 20 corresponding to the above electrodes, are not shown in the figure, they are disposed along the direction perpendicular to the sheet of drawing.
The circumference portions 221A, 221B, 221C, 221D of the electrostatic supporting electrode 221 in the first pair are corresponding to the electrode portions 200A, 200B, 200C, 200D on the upper surface of the gyro rotor 20; the circumference portions 231A, 231B, 231C, 231D of the electrostatic supporting electrode 231 in the first pair are corresponding to the electrode portions 200Axe2x80x2, 200Bxe2x80x2, 200Cxe2x80x2, 200Dxe2x80x2 on the lower surface of the gyro rotor 20; the circumference portions 223A, 223B, 223C, 223D of the electrostatic supporting electrode 223 in the third pair are corresponding to the electrode portions 200A, 200B, 200C, 200D on the upper surface of the gyro rotor 20; the circumference portions 233A, 233B, 233C, 233D of the electrostatic supporting electrode 233 in the third pair are corresponding to the electrode portions 200Axe2x80x2, 200Bxe2x80x2, 200Cxe2x80x2, 200Dxe2x80x2 on the lower surface of the gyro rotor 20; The second pair of the electrostatic supporting electrodes, and those for the fourth pair will be the same as described above.
A manner in which the control direct-current voltages are applied to the electrostatic supporting electrodes will be described. The circumference portions 221A, 221C of the first comb-shaped portion 221-1 of the first pair of the electrostatic supporting electrode 221 are connected to a direct-current voltage xe2x88x92V1A through an adder 36xe2x88x921A; the circumference portions 221B, 221D of the second comb-shaped portion 221-2 are connected to a direct-current voltage +V1A through an adder 36+1A; the circumference portions 231A, 231C of the first comb-shaped portion 231-1 of the first pair of the electrostatic supporting electrode 231 are connected to a direct-current voltage xe2x88x92V1B through an adder 36xe2x88x921B; and the circumference portions 231B, 231D of the second comb-shaped portion 231-2 are connected to a direct-current voltage +V1B through an adder 36+1B.
Similarly, the circumference portions 223A, 223C of the first comb-shaped portion 223-1 of the third pair of the electrostatic supporting electrode 223 are connected to a direct-current voltage xe2x88x92V3A through an adder 36xe2x88x923A; the circumference portions 223B, 223D of the second comb-shaped portion 223-2 are connected to a direct-current voltage +V3A through an adder 36+3A; the circumference portions 233A, 233C of the first comb-shaped portion 233-1 of the third pair of the electrostatic supporting electrode 233 are connected to a direct-current voltage xe2x88x92V3B through an adder 36xe2x88x923B; and the circumference portions 233B, 233D of the second comb-shaped portion 233-2 are connected to a direct-current voltage +V3B through an adder 36+3B.
Although not shown in the figure, the circumference portions 222A, 222C of the first comb-shaped portion 222-1 of the second pair of the electrostatic supporting electrode 222 are connected to a direct-current voltage xe2x88x92V2A; the circumference portions 222B, 222D of the second comb-shaped portion 222-2 are connected to a direct-current voltage +V2A; the circumference portions 232A, 232C of the first comb-shaped portion 232-1 of the second pair of the electrostatic supporting electrode 232 are connected to a direct-current voltage xe2x88x92V2B; and the circumference portions 232B, 232D of the second comb-shaped portion 232-2 are connected to a direct-current voltage +V2B.
Similarly, the circumference portions 224A, 224C of the first comb-shaped portion 224-1 of the fourth pair of the electrostatic supporting electrode 224 are connected to a direct-current voltage xe2x88x92V4A; the circumference portions 224B, 224D of the second comb-shaped portion 224-2 are connected to a direct-current voltage +V4A; the circumference portions 234A, 234C of the first comb-shaped portion 234-1 of the fourth pair of the electrostatic supporting electrode 234 are connected to a direct-current voltage xe2x88x92V4B; and the circumference portions 234B, 234D of the second comb-shaped portion 234-2 are connected to a direct-current voltage +V4B.
Then, A manner in which the detection alternating-current voltages are applied to the electrostatic supporting electrodes will be described. The detection alternating-current voltages, AC1A, AC1B, AC3A, AC3B, which have been superimposed on the control direct-current voltages, are applied to the first pair and the third pair of the electrostatic supporting electrodes 221, 231; and 223, 233. As shown in the figure, the detection alternating-current voltages AC1A, AC1B, are applied to the first pair of the adders 36xe2x88x921A, 36+1A, and 36xe2x88x921B, 36+1B, and the detection alternating-current voltages AC3A, AC3B are applied to the third pair of the adders 36xe2x88x923A, 36+3A, and 36xe2x88x923B, 36+3B. Similarly, the detection alternating-current voltages AC2A, AC2B, and AC4A, AC4B are applied to the second and the fourth pairs of the adders, respectively. The above described detection alternating-current voltages AC1A, AC1B, AC3A, AC3B, AC2A, AC2B, and AC4A, AC4B are respectively expressed by the following equations:
[Numerical Expression 1]
AC1A=xe2x88x92EXxe2x88x92Excex8xe2x88x92EZ
AC1B=xe2x88x92EX+Excex8+EZ
AC3A=+EX+Excex8+EZ
AC3B=+EXxe2x88x92Excex8+EZ
[Numerical Expression 2]
AC2A=xe2x88x92EYxe2x88x92Excfx86xe2x88x92EZ
AC2B=xe2x88x92EY+Excfx86+EZ
xe2x80x83AC4A=+EY+Excfx86xe2x88x92EZ
AC4B=+EYxe2x88x92Excfx86+EZ
where individual terms on the right side for the detection alternating-current voltages AC1A, AC1B, AC3A, AC3B; and AC2A, AC2B, AC4A, AC4B are expressed as follows:
[Numerical Expression 3]
+EX=E0 cos (xcfx891t+xcex61)
xe2x88x92EX=E0 cos (xcfx891t+xcex71)
+EY=E0 cos (xcfx892t+xcex62)
xe2x88x92EY=E0 cos (xcfx892t+xcex72)
+EZ=E0 cos (xcfx893t+xcex63)
xe2x88x92EZ=E0 cos (xcfx893t+xcex73)
+Excex8=E0 cos (xcfx894t+xcex64)
xe2x88x92Excex8=E0 cos (xcfx894t+xcex74)
+Excfx86=E0 cos (xcfx895t+xcex65)
xe2x88x92Excfx86=E0 cos (xcfx895t+xcex75)
where xc2x1EX represent voltage components for detecting a linear displacement xcex94X in the X-axis direction of the gyro rotor 20; xc2x1EY represent voltage components for detecting a linear displacement xcex94Y in the Y-axis direction of the gyro rotor 20; xc2x1EZ represent voltage components for detecting a linear displacement xcex94Z in the Z-axis direction of the gyro rotor 20; xc2x1Excex8 represent voltage components for detecting a rotational displacement xcex94xcex8 around the Y-axis of the gyro rotor 20; and xc2x1Excfx86 represent voltage components for detecting a rotational displacement xcex94xcfx86 around the X-axis of the gyro rotor 20.
xcfx891, xcfx892, xcfx893, xcfx894, and xcfx895 are displacement detection frequencies. Further, the sign of xc2x1EX, xc2x1EY, xc2x1EZ, xc2x1Excex8, and xc2x1Excfx86 shows the phase difference of 180 degrees. Therefore, the phase differences xcex6, xcex7 have the relationship expressed as follows:
[Numerical Expression 4]
xcex71=xcex61xc2x1180xc2x0
xcex72=xcex62xc2x1180xc2x0
xcex73=xcex63xc2x1180xc2x0
xcex74=xcex64xc2x1180xc2x0
xcex75=xcex65xc2x1180xc2x0
Referring to FIG. 4, the principle of the displacement-detection system according to the present example will be described. FIG. 4 shows the equivalent circuit of the restraining control system and the rotor drive system. In the equivalent circuit of the restraining control system, capacitors are substituted for the first and the third pairs of electrostatic supporting electrodes 221, 231 and 223, 233, and the corresponding electrode portions 200A, 200Axe2x80x2, 200C, 200Cxe2x80x2 of the gyro rotor 20. As described above, the capacitance between the first comb-shaped portions 221-1 and the first and third electrode portions 200A, 200C is equal to that between the second comb-shaped portions 221-2 and the second and fourth electrode portions 200B, 200D at the first electrostatic supporting electrode 221 in the first pair of the electrostatic supporting electrodes 221, 231, and the value of the capacitance is C1A; and the capacitance between the first comb-shaped portions 231-1 and the first and third electrode portions 200Axe2x80x2, 200Cxe2x80x2 is equal to that between the second comb-shaped portions 231-2 and the second and fourth electrode portions 200Bxe2x80x2, 200Dxe2x80x2 at the second electrostatic supporting electrode 231, and the value of the capacitance is C1B.
Similarly, the capacitance between the first comb-shaped portions 223-1 and the first and third electrode portions 200A, 200C is equal to that between the second comb-shaped portions 223-2 and the second and fourth electrode portions 200B, 200D at the first electrostatic supporting electrode 223 of the third pair of electrostatic supporting electrodes 223, 233, and the value of the capacitances is C3A, and capacitance between the first comb-shaped portions 233-1 and the first and third electrode portions 200Axe2x80x2, 200Cxe2x80x2 is equal to that between the second comb-shaped portions 233-2 and the second and fourth electrode portions 200Bxe2x80x2, 200Dxe2x80x2 at the second electrostatic supporting electrode 233, and the value of the capacitances is C3B.
A cross section, taken along the YZ plane, of the gyro apparatus according to the present example is not shown in the figure. However, a similar argument will be applied to the second and fourth pairs of electrostatic supporting electrodes 222, 232; and 224, 234, which are disposed along the Y axis, and the corresponding second and the fourth parts P2, P4 of the gyro rotor 20.
Capacitance of the capacitor, comprising the displacement-detection electrodes 226, 236, and the corresponding displacement-detection electrode portion 200F, 200Fxe2x80x2 of the gyro rotor 20 respectively, are assumed to be CFA, and CFB, respectively.
Assume that the gyro rotor 20 is linearly displaced in the X-axis direction by xcex94X, linearly displaced in the Y-axis direction by xcex94Y, and linearly displaced in the Z-axis direction by xcex94Z and that the gyro rotor 20 is rotationally displaced around the Y-axis by a rotating angle of xcex94xcex8, rotationally displaced around the X axis by a rotating angle of xcex94xcfx86. When it is supposed that such displacements of the gyro rotor 20 are sufficiently small, the capacitance of individual capacitors is expressed by the following equation:
[Numerical Expression 5]
C1A=C0 (1+xcex94X+xcex94Z+xcex94xcex8)
C1B=C0 (1+xcex94Xxe2x88x92xcex94Zxe2x88x92xcex94xcex8)
C2A=C0 (1+xcex94Y+xcex94Z+xcex94xcfx86)
C2B=C0 (1+xcex94Yxe2x88x92xcex94Zxe2x88x92xcex94xcfx86)
C3A=C0 (1xe2x88x92xcex94X+xcex94Zxe2x88x92xcex94xcex8)
C3B=C0 (1xe2x88x92xcex94Xxe2x88x92xcex94Z+xcex94xcex8)
C4A=C0 (1xe2x88x92xcex94Y+xcex94Zxe2x88x92xcex94xcfx86)
C4B=C0 (1xe2x88x92xcex94Yxe2x88x92xcex94Z+xcex94xcfx86)
where C0 represents the electrostatic capacity obtained when all the displacements of the gyro rotor 20 is zero. Conversely, individual displacements xcex94X, xcex94Y, xcex94Z, xcex94xcex8, and xcex94xcfx86 may be represented by the capacitance of the capacitors, using the above expression:
[Numerical Expression 6]
xcex94X=(xc2xcC0) (C1A+C1Bxe2x88x92C3Axe2x88x92C3B)
xcex94Y=(xc2xcC0) (C2A+C2Bxe2x88x92C4Axe2x88x92C4B)
xcex94Z=(xc2xcC0) (C1Axe2x88x92C1B+C3Axe2x88x92C3B)
=(xc2xcC0) (C2Axe2x88x92C2B+C4Axe2x88x92C4B)
xcex94xcex8=(xc2xcC0) (C1Axe2x88x92C1Bxe2x88x92C3A+C3B)
xcex94xcfx86=(xc2xcC0) (C2Axe2x88x92C2Bxe2x88x92C4A+C4B)
The control direct current voltages xc2x1V1A, xc2x1V1B, xc2x1V3A, and xc2x1V3B with the same magnitude but with the opposite polarities are applied to the two comb-shaped portions 221-1 and 221-2, 231-1 and 231-2, 223-1 and 223-2, 233-1 and 233-2 in the individual electrostatic supporting electrodes, whereby the potentials developed at the junctions Q1, Q2, Q3, Q4 (only Q1, and Q3 are shown in the figure) of the two pairs of capacitors become zero. Accordingly, since the control direct current voltages with the same magnitude but with the opposite polarities are applied to the comb-shaped portions of each pair of electrostatic supporting electrodes, the potential of the gyro rotor 20 becomes zero.
When the detection alternating-current voltages, AC1A, AC1B, AC2A, AC2B, AC3A, AC3B, and AC4A, AC4B, which have been superimposed on the control direct-current voltages, are individually applied to the first through the fourth pairs of the electro static supporting electrodes 221, 231, 222, 232, 223, 233, and 224, 234, the displacement-detection alternate-current iP is generated in the displacement-detection electrodes 226, 236. The above displacement-detection alternate-current iP is expressed by the following equation:
[Numerical Expression 7]
iP=Kxe2x80x2(C1AAC1A+C1BAC1B+C2AAC2A+C2BAC2B+C3AAC3A+C3BAC3B+C4AAC4A+C4BAC4B)
Kxe2x80x2=2 (CFA+CFB)s/(2C1A+2C1B+2C2A+2C2B+2C3A+2C3B+2C4A+2C4B+CFA+CFB)
where Kxe2x80x2 is a proportional constant, and s is a Laplacian operator. When the detection alternating-current voltages AC1A, AC1B, AC2A, AC2B, AC3A, AC3B, and AC4A, AC4B expressed by Numerical Expression 1, and Numerical Expression 2; and the capacitance C1A, C1B, C2A, C2B, C3A, C3B, and C4A, C4B expressed by Numerical Expression 5 are substituted into the above expression, the displacement-detection alternate-current iP is represented by the displacements after proper disposition. Consequently, when the gyro rotor 20 is linearly displaced by xcex94X in the X-axis direction, linearly displaced by xcex94Y in the Y-axis direction, linearly displaced by xcex94Z in the Z-axis direction, rotationally displaced by a rotating angle of xcex94xcex8 around the Y-axis, and rotationally displaced by a rotating angle of xcex94xcfx86 around the X-axis, the displacement-detection alternating-current iP is expressed by the following equation:
[Numerical Expression 8]
iP=KI (EXxcex94X+EYxcex94Y+2EZxcex94Z+Excex8xcex94xcex8+Excfx86xcex94xcfx86)
KI=xe2x88x928sC0(CFA+CFB)/(16C0+CFA+CFB)
where KI is a proportional constant, and s is a Laplacian operator. The above displacement-detection alternating-current iP is supplied to the preamplifier 35 through a resistor 36 with a resistance R, and converted into a displacement-detection alternating-current voltage VP. Such displacement-detection alternating-current voltage VP is represented by the following equation:
[Numerical Expression 9]
VP=VP(X)+VP(Y)+VP(Z)+VP(xcex8)+VP(xcfx86)
where individual terms in the right side are voltage components corresponding to individual displacements xcex94X, xcex94Y, xcex94Z, xcex94xcex8, and xcfx86, and are expressed by the following equation:
[Numerical Expression 10]
VP(X)=KIEXxcex94X=KV1E0xcfx891xcex94X sin(xcfx891t+xcex61)
VP(Y)=KIEYxcex94Y=KV2E0xcfx892xcex94Y sin(xcfx892t+xcex62)
xe2x80x83VP(Z)=KIEZxcex94Z=KV3E0xcfx893xcex94Z sin(xcfx893t+xcex63)
VP(xcex8)=KIExcex8xcex94xcex8=KV4E0xcfx894xcex94xcex8 sin(xcfx894t+xcex64)
VP(xcfx86)=KIExcfx86xcex94xcfx86=KV5E0xcfx895xcex94xcfx86 sin(xcfx895t+xcex65)
where KV1 through KV5 are constants defined by the capacitance C0, CFA, and CFB of the capacitor. As is evident from Numerical Expressions 9 and 10, the output voltage VP independently includes all the displacements of the gyro rotor 20. Therefore, when a desired voltage component is calculated based on Numerical Expression 9, a displacement corresponding to the above component is obtained. For example, even when two or more of linear displacements xcex94X, xcex94Y, xcex94Z, and rotational displacements xcex94xcex8, xcex94xcfx86 are superimposed, each displacement is obtained by calculating a voltage component corresponding to the displacement. Further, the above equation shows that the output voltage VP is amplitude-modulated according to individual displacement-detection frequencies xcfx891-xcfx895 corresponding to linear displacements xcex94X, xcex94Y, xcex94Z, and rotational displacements xcex94xcex8, xcex94xcfx86.
When linear displacements xcex94X, xcex94Y, xcex94Z, and rotational displacements xcex94xcex8, xcex94xcfx86 are obtained, control direct-current voltages are calculated based on the displacement. The control direct-current voltages are expressed by the following equation:
[Numerical Expression 11]
V1A=V0+xcex94V1A
xe2x80x83V1B=V0+xcex94V1B
V2A=V0+xcex94V2A
V2B=V0+xcex94V2B
V3A=V0+xcex94V3A
V3B=V0+xcex94V3B
V4A=V0+xcex94V4A
V4B=V0+xcex94V4B
V1A and V1B are control direct-current voltages applied to the first pair of electrostatic supporting electrodes 221, 231; V2A and V2B are control direct-current voltages applied to the second pair of electrostatic supporting electrodes 222, 232; V3A and V3B are control direct-current voltages applied to the third pair of electrostatic supporting electrodes 223, 233; and V4A and V4B are control direct-current voltages applied to the fourth pair of electrostatic supporting electrodes 224, 234.
V0 is a known reference voltage. Therefore, in order to obtain the control direct-current voltages, it is only required to obtain changed amounts of the above voltages xcex94V1A, xcex94V1B, xcex94V2A, xcex94V2B, xcex94V3A, xcex94V3B, and xcex94V4A, xcex94V4B. The above changed amounts may be obtained by calculation based on linear displacements xcex94X, xcex94Y, xcex94Z, and rotational displacements xcex94xcex8, xcex94xcfx86. In the first place, forces Fx, Fy, Fz made to be dimensionless, and torques Txcex8, Txcfx86 are calculated from linear displacements xcex94X, xcex94Y, xcex94Z, and rotational displacements xcex94xcex8, xcex94xcfx86. Description of the dimensionless calculation in detail will be omitted. Refer to the above application for the detailed description.
In the calculation for obtaining the changed amounts of the control direct current voltages based on the dimensionless forces Fx, Fy, Fz, and torques Txcex8, Txcfx86, the required conditional expressions, considering that of variables (changed amount), are not sufficient. Accordingly, further conditional expression is provided for changed amounts xcex94V1A, xcex94V1B, and, xcex94V3A, xcex94V3B; xcex94V2A, xcex94V2B, and, xcex94V4A, xcex94V4B.
[Numerical Expression 12]
xcex94V1A+xcex94V1B+xcex94V3A+xcex94V3B=0
xcex94V2A+xcex94V2B+xcex94V4A+xcex94V4B=0
The changed amounts of the control direct-current voltages xcex94V1A through xcex94V4B are calculated based on the above conditional expression. The above calculation is expressed as follows:
[Numerical Expression 13]
xcex94V1A=(V0/4) (Fx+Fz/2+Txcex8)
xcex94V1B=(V0/4) (Fxxe2x88x92Fz/2xe2x88x92Txcex8)
xcex94V2A=(V0/4) (Fy+FZ/2+Txcfx86)
xcex94V2B=(V0/4) (Fyxe2x88x92FZ/2xe2x88x92Txcfx86)
xcex94V3A=(V0/4) (xe2x88x92Fx+Fz/2xe2x88x92Txcex8)
xcex94V3B=(V0/4) (xe2x88x92Fxxe2x88x92Fz/2+Txcex8)
xcex94V4A=(V0/4) (xe2x88x92Fy+Fz/2xe2x88x92Txcfx86)
xcex94V4B=(V0/4) (xe2x88x92Fyxe2x88x92Fz/2+Txcfx86)
The dimensionless forces Fx, Fy, Fz, and torques Txcex8, Txcfx86 are supplied to the gyro-acceleration-output calculation unit 145, in which external accelerations xcex1x, xcex1y, xcex1z, and angular velocities dxcex8/dt, dxcfx86/dt are calculated. The external accelerations and the angular velocities are expressed as follows:
[Numerical expression 14]
xcex1X=Fx/mg
xcex1Y=Fy/mg
xcex1Z=Fz/mg
dxcex8/dt=Txcex8/H
dxcfx86/dt=Txcfx86/H
where m represents the mass of the gyro rotor 20; g represents the gravitational acceleration; and H represents a spin angular momentum of the gyro rotor 20.
Next, the rotor drive system in the gyro apparatus will be described. As shown in FIGS. 2 through 4, the rotor drive system according to the present example includes: driving electrode portions 200E and 200Exe2x80x2 formed on the upper surface and the lower surface of the gyro rotor 20; driving electrodes 225, 235 formed on the upper bottom member 22 and the lower bottom member 24 of the gyro case 21; and the rotor driving unit 160. The rotor drive system according to the present example is configured such that instruction signals from the sequence control unit 170 are input to the system, and the driving voltages are supplied to the driving electrodes 225, 235 to start, rotate, and stop the gyro rotor 20.
Further, as described above, the driving electrode portion 200E of the gyro rotor 20 and the driving electrode 225; the driving electrode portion 200Exe2x80x2 and the driving electrode 235 are respectively disposed in a row on the circumference with the same radius, and each of them comprises a plurality of sectorial portions in the same shape, as shown in FIG. 1B.
The driving electrode portions 200E and 200Exe2x80x2, and the driving electrodes 225, 235 constitute three-phase electrode. According to the present example, the upper driving electrode portion 200E of the gyro rotor 20 includes four sectorial portions which are spaced apart from each other by a central angle of ninety degrees, and the lower driving electrode portion 200Exe2x80x2 of the gyro rotor 20 includes four sectorial portions which are spaced apart from each other by a central angle of ninety degrees.
Corresponding to the above described electrode portions, the upper driving electrode 225 of the gyro case 21 includes twelve sectorial portions spaced apart from each other by the same central angle; and the lower driving electrode 235 of the gyro case 21 includes twelve sectorial portions spaced apart from each other by the same central angle. Each of twelve driving electrodes 225 or 235 comprises four sets of sectorial portions, respectively, and individual sectorial portions include three sectorial portions, that is, the first-phase, the second-phase, and the third-phase sectorial portions.
The corresponding phases of the sectorial portions of each set of the driving electrode 225 or 235 are electrically connected to each other. For example, the four first-phase driving electrodes 225 or 235 are connected to each other; the four second-phase driving electrodes 225 or 235 are connected to each other; and the four third-phase driving electrodes 225 or 235 are connected to each other.
The three-phase driving voltage is supplied to the above three-phase common terminal. The driving voltage may be a step-like voltage or a pulse voltage. The above voltage is sequentially switched to the adjacent four sectorial portions of the subsequent phase. The switching of the driving voltage is performed synchronized with the rotation of the gyro rotor 20, whereby the gyro rotor 20 is rotated at a high speed. Since the cavity 26 of the gyro case 21 is maintained to be a high vacuum, the driving voltage may be either cut off or continuously supplied, once the gyro rotor 20 rotates at a high speed.
The driving electrode portions 200E, 200Exe2x80x2, and the driving electrodes 225, 235, constituting the three-phase electrode, may be configured to include more sectorial portions. For example, the driving electrode portions 200E, 200Exe2x80x2 may respectively include five sectorial portions, and concurrently the individual driving electrodes 225, 235 are configured to include five sets (fifteen pieces), corresponding to the above.
An equivalent circuit of the rotor drive system is shown at the right side of FIG. 4. Capacitors are substituted for the driving electrode portion 200E of the gyro rotor 20, and the driving electrode 225 of the gyro case 21; and capacitors are substituted for the driving electrode portion 200Exe2x80x2 of the gyro rotor 20, and the driving electrode 235 of the gyro case 21. The driving direct-current voltages VR1, VR2, VR3 for rotating the gyro rotor 20, and the detection alternating-current voltages ACR1, ACR2, ACR3 for detecting the rotational angles of the gyro rotor 20 are applied to each capacitor.
Referring to FIG. 5, the operation of a driving motor according to the present example will be described in detail. FIG. 5 shows the state where the upper driving electrode portion 200E of the gyro rotor 20, which are circumferentially disposed in actual practice, and the upper driving electrode 225 of the gyro case 21, which is corresponding to the above electrode portions, are linearly disposed.
The upper driving electrode portion 200E of the gyro rotor 20 includes four sectorial portions 200E-1, 200E-2, 200E-3, 200E-4, which are spaced apart from each other by a central angle of ninety degrees. Corresponding to this, the upper driving electrode 225 of the gyro case 21 includes twelve sectorial portions; each sectorial portion comprises four sets; and individual sets include three, that is, three phase sectorial portions. The first-phase, the second-phase, and the third-phase sectorial portions of each set are denoted by reference numerals 225-1, 225-2, and 225-3, respectively.
The four first-phase sectorial portions 225-1 are electrically connected to each other; the four second-phase sectorial portions 225-2 are electrically connected to each other; and the four third-phase sectorial portions 225-3 are electrically connected to each other.
When the instruction signal from the sequence control unit 170 is supplied to the rotor driving unit 160, the driving direct-current voltages VR1, VR2, VR3, and the detection alternating-current voltages ACR1, ACR2, ACR3 are applied to individual three-phase driving electrodes 225-1, 225-2, 225-3.
The driving direct-current voltages VR1, VR2, VR3 are sequentially applied to the first-phase, second-phase, and third-phase electrodes 225-1, 225-2, 225-3 at every predetermined switching time xcex94t, whereby the gyro rotor 20 rotates around the central axis, that is, around the spin axis by 360/12 degrees=30 degrees at every switching time xcex94t.
Waveforms shown in the lower part of FIG. 5 represents rotational-angle detection currents generated in the displacement-detection electrodes 226, 236, or, rotational-angle detection voltages ACQ1, ACQ2, ACQ3 corresponding to the above currents. The rotational angle of the gyro rotor 20 is detected by such rotational-angle detection signals ACQ1, ACQ2, ACQ3.
For example, when the driving direct-current voltage VR1 is applied to the first-phase driving electrode 225-1, the gyro rotor 20 rotates around the central axis, until the four driving electrode portions 200E-1, 200E-2, 200E-3, 200E-4 are matched with the first-phase driving electrodes 225-1, 225-1, 225-1, 225-1, that is, by thirty degrees. Then, when the driving direct-current voltage VR2 is applied to the second-phase driving electrode 225-2, the gyro rotor 20 rotates around the central axis until the four driving electrode portions 200E-1, 200E-2, 200E-3, 200E-4 are matched with the second-phase driving electrodes 225-2, 225-2, 225-2, 225-2, that is, by thirty degrees.
In the restraining control system of the gyro apparatus, restraining forces or restoring forces are generated to return the gyro rotor to the reference position when the gyro rotor is deviated from the reference position. The restraining forces are electrostatic supporting forces of the capacitor comprising the electrode portions of the gyro rotor and the electrostatic supporting electrodes of the gyro case. For example, the restraining forces in the X-axis, Y-axis, and Z-axis directions are expressed by the following equation:
[Numerical Expression 15]
fx=(CV2)/(2L)
fy=(CV2)/(2L)
fz=(CV2)/(2xcex6)
where C represents a capacitance of a capacitor; V represents a voltage; L represents a dimension of a side of a capacitor; and xcex6 represents a space between capacitors. Rotational moment fxcex8 around the Y axis and rotational moment fxcfx86 around the X axis are obtained by multiplying the restraining force fz in the Z-axis direction by the arm r of the moment.
The electrostatic supporting voltage V for generating the restraining force is a sum of the reference voltage V0 and the changed amount xcex94V as shown by Numerical Expression 11, and the above changed amount is smaller than the reference voltage V0. Therefore, when the voltage V is assumed to be equal in each equation of Numerical Expression 15, the restraining force is represented as a function of the dimension L and the space xcex6 of the capacitor. When it is assumed that the dimension of one side of the capacitor is about 30 micrometers and the space of the capacitor is about 5 micrometers, the restraining forces in the X-axis and Y-axis directions are about six times smaller than that of the Z-axis direction.
Therefore, there have been a disadvantage that the accuracy and sensitivity of the restraining control in the X-axis and Y-axis directions are lower than those of the restraining control in the Z-axis direction and around the X axis and Y axis.
Further, for example, when the acceleration of equal magnitude are applied in the X-axis and Y-axis, Z-axis directions, the restraining forces fx, fy in the X-axis and Y-axis directions; the rotational moment fxcex8 around the Y-axis; and the rotational moment fxcfx86 around the X-axis increase. Accordingly, the changed amounts xcex94V1A through xcex94V4B of the control direct-current voltages expressed by Numerical Expression 13 become large, and this requires a high voltage to be generated.
Accordingly, the object of the present invention is to perform the restraining control in the X-axis and Y-axis directions with the same level of accuracy and sensitivity as those of the restraining control in the Z-axis direction and around the X-axis and Y-axis.
According to the present invention, an acceleration-detecting type gyro apparatus comprises:
a gyro case having a Z axis along the direction of a central axis, and X and Y axes perpendicular to the Z axis;
a gyro rotor which is supported within the gyro case by electrostatic supporting force such that the gyro rotor is not in contact with the gyro case, and has a spin axis in the central axis direction;
a plurality of electrostatic supporting electrodes which are spaced apart from the gyro rotor, and to which control voltages are applied;
a rotor drive system for rotating the gyro rotor around the spin axis at high speed;
a displacement-detection system for detecting linear displacements in the X-axis, Y-axis, and Z-axis directions, and rotational displacements around the Y and X axes of the gyro rotor; and
a restraining control system having a feedback loop for correcting the control voltages so that displacements detected by the displacement-detection system become zero, in which
the gyro rotor is annular-shaped, and the electrostatic supporting electrodes are disposed in the manner of surrounding the gyro rotor.
Accordingly, the magnitude of the restraining forces in the X-axis and Y-axis directions are on the same level as that of the restraining force in the Z-axis direction and torques around the X axis and Y axis, whereby the restraining control in the X-axis and Y-axis directions may be performed with the same levels of sensitivity and accuracy as those in the Z-axis direction and around the X-axis and Y-axis.
According to the present invention, the gyro rotor in the gyro apparatus is constituted to have a rectangular cross section formed of an upper surface, a lower surface, an inner circumference, and an outer circumference; the electrostatic supporting electrodes are provided in parallel to the upper surface, lower surface, inner circumference, and outer circumference. Therefore, sufficiently large electrostatic supporting forces may be generated by capacitors formed of the electrostatic supporting electrodes, the upper surface, lower surface, inner circumference, and outer circumference of the gyro rotor.
According to an embodiment of the present invention, the rotor drive system in the gyro apparatus comprises a plurality of rotor-driving electrodes which are provided corresponding to the upper and lower surfaces of the gyro rotor; a plurality of concave portions are provided on the upper and lower surfaces of the gyro rotor; and land portions between the concave portions are provided corresponding to the rotor-driving electrodes. According to another embodiment of the present invention, the rotor drive system in the gyro apparatus comprises a plurality of rotor-driving electrodes which are provided on the upper and lower surfaces of the gyro rotor; a plurality of through holes connecting the upper surface and the lower surface are provided in the gyro rotor; and land portions between the through holes are provided corresponding to the rotor-driving electrodes.
Accordingly, the rotor-driving forces in the circumferential direction may be efficiently generated.
According to the present invention, the displacement-detection system in the gyro apparatus comprises a plurality of displacement-detection electrodes which are spaced apart from the gyro rotor, in which the displacement-detection alternating-current voltages superimposed on the control voltages are applied to the electrostatic supporting electrodes and displacement-detection currents generated in the displacement-detection electrodes are detected by the displacement-detection alternating-current voltages, whereby the displacement of the gyro rotor is calculated.
According to the present invention, in the gyro apparatus, a plurality of the displacement-detection alternating-current voltages are constituted to be alternating-current voltages with different frequencies.
According to the present invention, in the gyro apparatus, a plurality of the displacement-detection alternating-current voltages are alternating-current voltages having the same frequency with different phases.